北方森林细根对氮沉降和二氧化碳浓度升高的响应

北方森林是全球第二大生物群区,约占全球森林面积的30%,尽管其细根生物量仅占森林生态系统很小的一部分,但其周转率更快,更易分解,因此,其对土壤碳循环和大气CO_2通量贡献很大。笔者综述了氮沉降和CO_2浓度升高的背景数据,总结了细根对二者变化的响应,主要从细根的形态特征、解剖结构和生理功能方面入手,探讨了其对氮沉降和CO_2浓度升高的响应。结论如下:(1)大气氮沉降量一直处于上升状态,与人类活动密切相关的有机氮量所占比例逐渐加大,而无机氮中NH_4~-N和NO_3~-N的变化趋势表现不同;(2)大气CO_2浓度一直呈上升趋势,细根形态特征、解剖结构和生理功能对其表现出明显的响应;(3)树种、年龄、土壤类型等都会改变细根形态、解剖结构和生理功能对氮沉降和CO_2浓度升高的响应结果,但改变的程度不同。研究结果可为北方森林乃至温带森林生态系统功能对氮沉降和CO_2浓度升高的响应提供参考依据和数据支持。

Response of Fine Root to Nitrogen Deposition and Elevated Atmospheric CO2 Concentration in Boreal Forest

Boreal forest is the second largest biome in the world, accounting for about 30 percent of the global forest area. Although fine root biomass accounts for only a small fraction of the total in the boreal forests, their turnover rates are faster and more easily decomposed, so they contribute more to soil carbon cycle and atmospheric carbon flux. In this paper, we summarized the changes of nitrogen (N) deposition and CO2 concentration, and summarized and compared the results of the fine root correlation research, and discussed the response of the morphology, anatomical structure and physiological function of the fine root to N deposition and CO2 concentration changes. The results are as follows: (1) China''s atmospheric N deposition has been on the rise, and the proportion of organic N is closely related to human activities gradually increased, while the inorganic nitrogen in the NH4-N and NO3-N trends are different; (2) The atmospheric CO2 concentration has been on the rise and may decline in the future, and the fine root morphological characteristics, anatomical structure and physiological function showed the obvious response to the two factors. (3) Tree species, age, soil types will affect the response of the fine root morphology, anatomical structure and physiological functions to nitrogen deposition and elevated CO2 concentration, and there are different changes in performance. This article can provide the reference basis and data support for the response of boreal forest and temperate forest ecosystem function to elevated nitrogen deposition and CO2 concentration.